Anchor for securing safety device

ABSTRACT

An anchor ( 1 ) is provided for securing at least one safety device to a structure ( 40, 70, 97 ), the anchor ( 1 ) including: a) a shaft ( 12 ) terminating in engagement means ( 11 ), such as an eyelet, the shaft ( 12 ) located in the structure ( 40, 70, 97 ) and adapted to reciprocate between a retracted position in the structure ( 40, 70, 97 ) and an extended position whereby the engagement means ( 11 ) is capable of extending beyond the external surface of the structure ( 40, 70, 97 ); b) stop means ( 31 ) adapted to limit the extent to which the engagement means ( 11 ) may be extended beyond the surface of the structure ( 40, 70, 97 ); and c) resiliently deformable means ( 14 ) such as a compressible rubber sleeve, adapted to coact with the shaft ( 12 ) and the stop means ( 31 ) to resist axial extension of the shaft ( 12 ) up to the extent determined by the stop means ( 31 ).

TECHNICAL FIELD

[0001] This invention relates to an anchor for securing at least one safety device to a structure, such as a building structure. More particularly, the invention relates to an anchor for securing at least one safety device located outside of a building to the internal wall of the building.

BACKGROUND ART

[0002] Conventional roof anchoring devices require access to a roof support structure such as a purlin or rafter. Direct access to the support structure is generally required and involves mounting the roof anchor prior to the application of the external covering of the roof such as tiles, sarking or sheeting so that, on application of the external covering to the support structure, the roof anchor extends proud of the external covering.

[0003] Anchoring devices for existing building structures have been more problematic and work associated with eternal walls of buildings have generally required the temporary installation of scaffolding, both to support the operator and to guard against falls. More permanent anchor points mounted to the sides of buildings are discouraged because of their unattractive appearance and the lack of structurally sound members on which to locate the anchor.

[0004] Moreover, prior art anchors are generally fixed constructions which may successfully arrest the descent of a falling operator but still result in injury due to the sudden deceleration by the victim once the worker's descent is arrested by the safety device.

[0005] The above description of the prior art is not intended to be, nor should it be interested as, an indication of the common general knowledge pertaining to the invention, but rather, to assist the person skilled in the art in understanding the developmental process which led to the invention.

DISCLOSURE OF THE INVENTION

[0006] Accordingly, the invention provides in one aspect an anchor for securing at least one safety device to a structure, the anchor including:

[0007] a) a shaft terminating in engagement means, said shaft located in the structure and adapted to reciprocate between a retracted position in the structure and an extended position whereby the engagement means is capable of extending beyond the external surface of the structure;

[0008] b) stop means adapted to limit the extent to which the engagement means may be extended beyond the structure's surface; and

[0009] c) resiliently deformable means adapted to coact with the shaft and the stop means to resist axial extension of the shaft up to the extent determined by the stop means.

[0010] The structure may include a building structure. The building structure may be in the process of being built, or may be the subject of maintenance or renovation activities. The building may be a commercial or domestic structure and the invention is applicable to any type of building structure, requiring only that the structure be capable of supporting the load constraints involved. Safety devices should be installed in compliance with the current safety codes of practice for working at heights in the particular jurisdiction concerned. Structural members forming part of the structure nay include purlins, structural beams, concrete walls, ceilings and floors, whether reinforced or not, and the like. In a particular aspect of this invention, the structure is a concrete wall, ceiling or floor, or a solid metal plate member.

[0011] The safety device may include a range of devices adapted to secure a worker or an object. The safety device may include a railing. The safety device may include a railing to which a safety harness or a runner may be secured. The safety device may include a safety harness affixed to the anchor, such as by a rope or cable. In particular, the st device includes safety harnesses, fill arrestors, work positioning belts and the like. Preferably, where the safety device is a harness, crotch and sternum support should be provided.

[0012] In a preferred application of the invention, the anchor is adapted to be located on an internal wall adjacent a wall opening, such as a window. The operator may be able to secure his safety device to the anchor on the internal wall of the building and to gain access to the outside of the building, secured by one or more anchors, via the wall opening.

[0013] The anchor may also be installed during the construction of the structure. For example, the structure may comprise a cast concrete slab into which one or more anchors may be placed by putting in position prior to pouring and setting the concrete. To assist in the correct orientation of the anchor, the shaft may be aligned by magnetic means fixed to, for example, metal reinforcing.

[0014] The shaft may be a range of configurations and dimensions, provided that the shaft is relatively elongate and capable of permitting the engagement means to be extended beyond the line of the surface of the structure. In cross section the shaft may be circular, ova or polygonal, such as square in cross section. The shaft may be of hollow construction, but is preferably solid. The shaft may be made from a range of materials having sufficient strength for the purpose. For example, the shaft may be made from high strength polymeric materials, optionally reinforced with metal members, such as an internal metal core. Preferably, the shaft is solid metal, such as sunless steel. The shaft may be of constant cross section or may taper towards one end. The shaft may taper to the end proximal to the engagement means. Preferably, the shaft is of constant cross section and of solid metal construction.

[0015] The engagement reams may include any suitable feature adapted to engage the safety device. For example, the engagement means may include a simple eyelet. The engagement means may include an engagement device for fastening the safety device to the anchor. For example, the engagement device may include a screw fastener, eyelet or closable hook as may be found in grappling, abseiling or boat rigging gear. The engagement means may support an anchorage line adapted to support a shuttle capable of running along a cable permanently attached to the structure, thereby enabling the worker to move along the anchorage line safely, without needing to unhook. The engagement means may engage a cable or lanyard, etc, in turn connected to the safety device. The engagement means may be integrally formed with the shaft. Alternatively, the engagement means may be separately formed and joined to the shaft, for example, by a threaded connection. Preferably, the engagement means is integrally formed with the shaft by standard metal casting methods, and most preferably is made of forged stainless steel.

[0016] The shaft may be adapted to deform to at least partially absorb the energy associated with the application of a high load, such as may be experienced with the sudden descent of a falling worker. Whilst the shaft may be capable of elastic deformation under non-operating loads, it is preferable that the shaft be plastically deformable, if deformable at all, only on application of high loads. Accordingly, it is preferable that the shaft be made from plastically deformable materials, such as metals, rather than polymeric materials which may be less adapted to plastically deform.

[0017] The shaft is preferably of such a length that the engagement means is able to be extended from a position proximal to the external surface of the structure to a position spaced from the external surface of the structure. To this purpose, the shaft may be located in a suitable bore within the structure, within which it is free to reciprocally travel in the bore. The anchor may further include a sleeve intermediate the shaft and the structure within which the shaft reciprocally travels. The sleeve preferably includes an internal bore or cavity which corresponds to the configuration of the shaft and other components of the anchor. For example, the sleeve may include a shallow recess proximal to the external surface of the structure to receive the engagement means in the retracted position.

[0018] The sleeve may include a dust cap at its end remote from the external surface of the structure to prevent the ingress of dust and grime into the sleeve cavity. The anchor may also include a housing for the engagement means. The housing may be integrally formed with the sleeve or may be separately formed and optionally coupled with the sleeve. For example, the housing may be coupled with the sleeve by threaded coupling, interference fit, other positive engagement or chemical bonding. The housing may define an internal cavity which corresponds directly to the configuration of the engagement means. For example, where the engagement means is an eyelet, the housing cavity may be correspondingly disc shaped, or spherically or hemispherically shaped. Preferably, the housing includes a removable or hinged cover which may be used to conceal the engagement means when not in use and removed or displaced when the anchor is required to be used. Preferably, the cover should be of low profile and fit in with the surrounding decor where applicable, and generally be of an aesthetically pleasing appearance.

[0019] The anchor may include one or more flanges ending laterally relative to the shaft whereby to determine the extent to which the anchor is sunk into the bore of the structure in the retracted position. For example, the housing may include lateral flanges, either radial or annular, which about the external surface of the structure immediately adjacent the anchor whereby to seat the anchor in a set position at a set depth relative to the external surface of the structure. Preferably, the lateral flange extends from the housing or the sleeve.

[0020] The stop means may be set in the structure when forming same or may be installed in an existing structure. The stop means may include break mea actuated by inertia prompted by the sudden acceleration of the shaft such as may occur upon application of a sudden high load. For example, the brake means may include pivoting cams. However, preferably the stop means is a fixed structure adapted to coact with the shaft and prevent its further travel beyond a predetermined extent. The shaft may include retaining means intermediate its length or at the end remote to the external surface of the structure. The retaining means may be adapted to come against, either directly or indirectly, the stop means whereby to prevent the shaft extending out further relative to the structure.

[0021] The resiliently deformable means may be located intermediate the length of the shaft, along the whole length of the shaft, or at one end or the other. The resiliently deformable means may be capable of at least partially absorbing the energy associated with the application of the high load by the compression or tensioning of the resiliently deformable means.

[0022] The resiliently deformable means may include a range of materials and/or configurations. The resiliently deformable means may include polymeric or rubberised materials capable of resiliently compressing or tensioning upon the application of a load. The resiliently deformable means is preferably adapted to progressively increasingly resist deformation. The resiliently deformable means may include a compression or tensioning spring. Preferably, the resiliently deformable means is compressible and is located intermediate the stop means and the retaining means.

[0023] Upon the extension of the engagement means remote from the external surface of the structure, the shaft may freely travel outwardly until the resiliently deformable means contacts the stop means. Upon fierier extension, the resiliently deformable means may compress or extend under tension to retard further evasion of the engagement means away from the external structure surface. Where the anchor includes retaining means, upon the shaft reaching the extended position the resiliently deformable means may be fully compressed or tensioned such that the retaining means can travel no further due to indirect or direct coaction with the stop means.

[0024] In a preferred arrangement, the retaining means may be engaged to the remote end of the shaft for example by threaded engagement, and may be adapted to travel within the sleeve. In this arrangement, the resiliently deformable means may be in the form of a compression spring abutting the retaining means and coming into contact with the stop means only then the shaft is extended, Where the retaining means is in the form of a threaded nut on the ed of a bolt portion of the shaft, there may bee provided a clip, such as a circlip, to prevent the retag means from unthreading from the shaft undesirably. The retaining means may be made of stainless steel or a composite material and is preferably a circular nut.

[0025] The resiliently deformable means may comprise a series of springs or a series of rubber components or a composite combination of metal, rubber and/or polymeric material.

[0026] The sleeve may be fixed in a corresponding bore in the structure by a number of standard means. For example, the sleeve may be chemically bonded to the bore in the structure by chemical bonding, interference fit or positive engagement such as by winged barbs. Preferably, the sleeve is non-removably installed in the bore of the structure. To assist in chemical bonding of the sleeve to the structure bore, the external surface of the sleeve may include surface features which facilitate such bonding. For example, the external surface of the sleeve may include a series of alternating lateral ridges and grooves or may be externally threaded to achieve this effect.

[0027] The housing may be threadably engaged to the external threaded surface of the sleeve. Alternatively, the internal Surface of the sleeve, particularly proximal to the housing may be threaded to enable the threaded engagement of the housing. Such an arrangement may also enable the threaded engagement of the stop means to the sleeve. To this purpose the stop means may include a correspondingly externally thread surface.

[0028] Similarly, the lower dust cap may be threadably engaged to the sleeve. However, in a particularly preferred embodiment the dust cap, particularly for vertical use, may include a magnet which is fitted to the sleeve and may be adapted to centre the shaft in the sleeve and may also be used to orientate the anchor in position before being embedded in concrete to be poured. To this purpose, the flange extending laterally from the housing may be exaggerated along a plane corresponding to that of the external surface of the structure whereby to facilitate the orientation of the anchor in position when forming up to pour concrete. The housing or cover can also include magnetic means whereby to give it the ability to be positioned onto steel form work and to hold the shaft in place wile pouring concrete.

[0029] In some situations the structure may be considered inadequate to cope with a high load applied to one region proximal to the external surface of the structure. In such circumstances, the invention provides in another arrangement an extension of the shaft. The shaft extension may extend completely through the structure to the opposing external surface. The extension may engage with the sleeve or the shaft. For example, where there is no sleeve provided, the extension may engage with the shaft.

[0030] The extension may comprise an extension shaft. The extension shaft may be threaded whereby to engage with a treaded sleeve and/or shaft or may be engaged with the shaft or sleeve in any other suitable matter familiar to the person skilled in the art.

[0031] The extension may include an adaptor coupling unit to adapt the size of the thread of the sleeve or shaft to the extension shaft. For example, the coupling unit may include a fist portion to couple with the sleeve or shaft and a second portion to couple with the extension shaft. Of course, the coupling unit may couple with the various components by means other than threaded engagement. Preferably, however, the, extension shaft and the coupling unit are coupled by threaded engagement.

[0032] The extension is particularly suitable for walls having at least a section of which includes a cavity and to this end the extension may include a spacer. The spacer may be adapted to extend substantially the length of the extension shaft and to resist the collapsing of the cavity wall. Preferably the spacer is in the form of a hollow lube such as a cylinder but may include various cross sectional configurations including circular and polygonal. The extension may terminate proud of the opposed structure surface with a locking means adapted to secure the anchor against the opposing external surface. For example, the locking means may include a lock nut and optionally a washer, the lock nut being adapted to couple with the extension shaft. The washer may be provided to resist the lock nut by effectively spreading the concentration of force applied by the lock nut to the opposed external surface.

[0033] The anchor may be adapted to be mounted to a steel beam or ire comprising a planar or substantially planar steel plate. The structure must be strong enough to withstand the significant forces applied thereto at the anchor point. In a preferred arrangement, the plate mounting may include a ale which engages with the shaft or sleeve and sandwiches the steel beam between the housing and the cradle.

[0034] In a particularly preferred embodiment the cradle, configured to correspond to the external configuration of the lower portion of the housing located within the internal surface of the structure, may be adapted to couple with the sleeve. The cradle may be adapted to abut against the internal surface of the structure and to cradle the lower portion of the housing in a recess defined by the lower portion of the housing. The lower portion of the housing may be adapted also to engage with the sleeve. Engagement of the various components may include positive engagement means such as treaded coupling or positive mechanical engagement means. The lateral flange may be adapted to rest on the external support surface whereby to ensure that the housing rests in fixed location on the structure. Preferably, the structure includes an aperture for receiving the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention may be better understood from the following non-limiting description of one or more of the preferred embodiments, in which:

[0036]FIG. 1 is a schematic side view of an eye bolt according to a first embodiment of the invention;

[0037]FIG. 2 is a schematic sectional view of a sleeve and housing according to another embodiment of the invention;

[0038]FIG. 3 is a schematic sectional view of an anchor according to the first embodiment, but shown in situ;

[0039]FIG. 4 is a schematic transverse section A-A of the anchor shown in FIG. 5;

[0040]FIG. 5 is a top plan view of the anchor according to the is embodiment;

[0041]FIG. 6 is a schematic sectional view of a cover;

[0042]FIG. 7 is a schematic sectional view of a housing and a sleeve according to the first embodiment;

[0043]FIG. 8 is a schematic sectional view of a housing and sleeve mountable to a steel plate;

[0044]FIG. 9 is a schematic sectional view of an anchor according to a third embodiment;

[0045]FIG. 10 is a schematic sectional view of an anchor according to a four embodiment shown in situ;

[0046]FIG. 11 is a top plan view of an anchor according to a fit embodiment; and

[0047]FIG. 12 is a schematic sectional view of a pair of anchors according to the fifth embodiment, shown respectively in retracted and extended positions in situ.

DETAILED DESCRIPTION OF DRAWINGS

[0048] Referring to FIG. 1 there is shown an eye bolt (10) including engagement means in the form of an eyelet (11) and a shaft (12) in the form of a bolt having a lower threaded portion (13). The eye bolt (10) is made from forged stainless steel. Resiliently deformable means being an energy absorbing unit made from a progressively compressible rubber compound is a compressible sleeve (14) adapted to slip on to the shaft (12). A circular stainless steel nut (15), being retaining means, is threadably mounted on to the threaded portion (13) of the shaft (12). To ensure the nut (15) is retained on he threaded portion (13) a circlip (16) is provided.

[0049] In FIG. 2 there is shown a housing and sleeve combination which may be used in the installation of an anchor during the setting of a structure such as concrete to be poured. The housing (20) is provided with a wide annular flange (21), the underside of which is adapted to rest on the setting structure. The housing (20) includes a hemispherical cradle recess (22), the upper rim of which supports the annular age (21). The lower portion of the cradle (22) includes a downwardly depending cylindrical threaded base adapted to threadably engage with a correspondingly threaded portion on the internal surface of the sleeve (24). A dust cap (25) may be provided to prevent the ingress of dust and other debris during the setting of the structure. In practice, the housing (20) performs as a positioning device which may be screwed in to the sleeve (24) to hold the sleeve (24) in the position required when forming the structure. The housing (20) and/or the dust cap (25) maybe magnetic whereby to enable the positioning of the sleeve (24) onto steel form work. Alternatively, the housing and sleeve combination may be screwed or otherwise secured into timber form work prior to pouring.

[0050] In FIG. 3 the anchor (1) is shown in situ whereby the underside of an annular flange (21 a) extending from the upper rim of the housing (20) rests on the external surface of the structure (40). The eyelet (11) is completely obscured by the cover (30) when in place whereby to present an aesthetically acceptable appearance adapted to match surrounding decor.

[0051]FIG. 5 shows a top plan view of an anchor (1) according to the first embodiment showing the eyelet (11) as if it were visible th the cover (30). FIG. 4 represents a section A-A shown in FIG. 5 and shows the completed anchor (1) wherein the eyebolt (10) is retractably received within sleeve (24). The housing (20) and cover (30) may be made from polymeric material, metal such as stainless steel, preferably forged stainless steel, or a composite material. Inserted within the sleeve immediately below the retracted position of the eyelet (11) is inserted a stop means in the form of an internal stop (31).

[0052] Referring to FIGS. 6 and 7, there is shown the cover (30) which may be hingedly attached to the upper rim of annular flange (21 a) by a hinge (60). Equally utilitarian would be a threaded engagement means in which the cover (30) is threadably engaged to the upper rim of annular flange (21 a). The purpose of the hinged cover (30) is to expose or to conceal the eyebolt (10) as red and to prevent the ingress of dust and other material entering the housing (20) and the sleeve (24). The internal stop (31) may be integrally formed with the internal surface of the housing (24) or may be a separate unit screwed or otherwise secured into the sleeve (24). In practice, the internal stop (31) prevents the eyebolt (10) from pulling further out of the sleeve (24) once the eyebolt (10) is fully extended. The sleeve (24) is adapted to be inserted in a bore in a structure such as a wall followed by the subsequent installation of the eyebolt (10). The sleeve (24) may be made from stainless steel, forged stainless steel, polymeric material or a composite material. The dust cap (25) may include a magnet fitted to hold the eyebolt (10) in place in coaxial alignment with the sleeve (24).

[0053] In FIG. 8 there is shown a housing (20) and sleeve combination for installation on a steel beam or fixture (70). There is additionally provided for this purpose a sandwiching lock nut (71) which corresponds in internal dimensions and configuration to the external configuration of the housing (20). The sandwiching lock nut (71) is adapted to readably engage with the external threaded surface of the sleeve (24) by means of an internally threaded cylindrical portion (72) depending from the lower portion of cup (73) of the sandwiching lock nut (71).

[0054] To install the sleeve (24) on the steel beam (70), a suitably sized bore is made in the steel beam (70) whereby to receive the housing (20) in snug relationship, the underside of the annular flange (21 a) resting on the external surface of the steel beam (70). The sandwiching lock nut (71) is screwed onto the outer surface of the sleeve (24) and the sleeve is then screwed on to the lower threaded portion (23) of the housing (20). The dust cap (25) may be fitted to the opposing end of the sleeve (24).

[0055] In FIG. 9 there is shown an extension (80) to anchor (1). The extension (80) is used to extend the sleeve (24), particularly for use in installing the anchor (1) in cavity walls. The extension (80) includes a threaded extension shaft (81) which may be threadably engaged to the sleeve (24) by means of an adaptive coupling unit (82). The coupling unit (82) includes a wide internally threaded upper portion (83) to engage the lower portion (13) of the sleeve (24) and an internally threaded lower portion (84) adapted to threadably engage with the extension shaft (81). The extension shaft (81) is inserted through a spacer (85) which is a hollow tube used to stop the cavity wall form collapsing when tightening a lock nut (86) over the end portion of the extension shaft (81). A washer (87) is provided to spread the concentration of force applied by the lock nut (86) to the opposed external surface of the structure.

[0056]FIG. 10 shows an anchor installed in a concrete structure wherein the housing is dispensed with and the arrangement includes only the eyebolt (10) and a sleeve (90). At the upper end of the sleeve (90) is provided an annular flange (91) depending laterally from the mouth of the sleeve (90). An O-ring (92) is fitted to the mouth of the sleeve (90) to prevent moisture entering into the sleeve (90) cavity.

[0057] Referring to FIG. 11, a alternative cover (95) is shown in which the cover (95) is held in place using rare earth magnets (96). Therefore the cover (95) may easily be removed by lifting the cover (95) with sufficient force to overcome the magnetic attraction and, as shown in FIG. 12, the eye bolt (10) may be simply pulled out for use.

[0058] In installing the anchor (1) all safety procedures must be complied with in accordance with the current safety codes of practice for working at heights. These include being attached to an anchor point, using approved safety equipment, a scaffold or a secured loader. Care should be taken in determining the number of anchor points. In considering the number of anchor points to be installed for a particular safety device or safety devices, the person skilled in the art will appreciate that the pendulum effect applies and care should be taken to arrange the anchor points and the ropes, cables and/or lanyards attaching the safety device or devices to the anchor points to minimise any such uncontrolled swinging action which might otherwise be experienced by a fallen worker. It should also be noted that the first anchor point must be in a position easily reached by a secured ladder or a man hole access point. The reinforcing steel (96) in the concrete (97) may be detected with a digital metal detector whereby to determine the appropriate 26 position of the bore hole for receiving the sleeve (24). If there is any doubt as to the structure adequacy of the anchorage, an engineer should be employed to make the assessment.

[0059] As an example, in installing the anchor (1), two holes may be drilled in the concrete (97), a first hole using a 55 mm hole saw drill to a depth of 20 mm, then a 28 mm hole may be drilled to a depth of 122 mm. Preparing the concrete cavity for receiving the housing (20), one can use a small chisel to remove the excess concrete to fit the shape of the housing (20). It should be ensured that the hole is moisture and dust free and any such dust may be removed using compressed air. The sleeve (24) maybe covered with a power-fast epoxy injection adhesive gel and inserted into the bore in the concrete (97). Care should be ten that the whole external surface of the sleeve (24) is secured within the concrete bore using sufficient, adhesive gel to achieve the purpose. The installed anchor (1) should be left for at least 48 hours for curing before testing. Each anchor (1) should be test after installation The test may consist of an ultimate pull out force proof loading to fifty percent of the design purpose of the anchor (1).

[0060] In practice, the safety device may be attached to the eyelet (11) and the secured worker my then proceed to his working position. If the worker should fall, the eyelet (11) will be dragged downwardly, at least some of the force including an outward axial component thereby drawing up the circular nut (15) towards the internal stop (31) whereby to sandwich the rubber sleeve (14) between the internal stop (31) and the circular nut (15). As the lower sleeve (14) compresses, energy from the fall is absorbed thereby minimising the jolt which the workman experiences when the cable or rope achieves its full extent.

[0061] Throughout the specification the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the context requires otherwise.

[0062] It will be appreciated by those skilled in the art that many modifications and variations may be made to the embodiments described herein without departing form the spirit or scope of the invention. 

1. An anchor for securing at least one safety device to a structure, the anchor including a) a shaft terminating in engagement means, said shaft located in the structure and adapted to reciprocate between a retracted position in the structure and an extended position whereby the engagement means is capable of extending beyond the external surface of the structure; b) stop means adapted to limit the extent to which the engagement means may be extended beyond the stucture's surface; c) resiliently deformable means adapted to coact with the shaft and the stop means to resist axial extension of the shaft up to the extent determined by the stop means.
 2. An anchor according to claim 1, wherein the anchor is capable of supporting a sudden high load applied through the safety device.
 3. An anchor according to claim 2, wherein the resiliently deformable means is capable of at least partially absorbing the energy associated with the application of the high load by the compression or tensioning of said resiliently deformable means.
 4. An anchor according to claim 2, wherein the shaft means is capable of at least partially absorbing the energy associated with the application of the high load by deforming.
 5. An anchor according to claim 4, wherein the shaft is adapted to plastically deform.
 6. An anchor according to claim 1, wherein the resiliently deformable means is a compression spring.
 7. An anchor according to claim 1, wherein the anchor is secured in the structure by a sleeve located in a bore within the structure.
 8. An anchor according to claim 7, wherein the stop means is located in the sleeve.
 9. An anchor according to claim 7, wherein the stop means is in the form of an annular shoulder on the internal surface of the shaft.
 10. An anchor according to claim 7, wherein the stop means is in the form of an insert adapted to threadably engage the internal surface of the shaft.
 11. An anchor according to claim 1, wherein the stop means has an internal bore adapted to permit the axial reciprocation of the shaft therethrough.
 12. An anchor according to claim 1, wherein the shaft includes reaming means adapted to coact with the stop means to limit the extent to which the engagement means may be extended beyond the structure's surface.
 13. An anchor according to claim 12, wherein the retaining means is located remotely from the structure's external surface and the stop means is adapted to is prevent the passage of the retaining member past the stop means.
 14. An anchor according to claim 1, wherein the anchor includes an extension adapted to extend through the structure so that the anchor is secured thereto by coacting with the opposed surfaces of the structure.
 15. An anchor according to claim 14, wherein the extension includes an extension shaft threadably engageable to the end of the shaft remote from the engagement means.
 16. An anchor according to claim 1, wherein the structure is a metal plate having a bore adapted to receive the anchor and the anchor has securement means capable of securing the anchor to the plate.
 17. An anchor according to claim 1, wherein the anchor includes a housing within which the engagement means is adapted to rest when the anchor is in the non-extended position.
 18. An anchor according to claim 1, wherein the anchor includes a cover adapted to obscure the engagement means when the anchor is in the non-extended position.
 19. An anchor according to claim 1, wherein the structure is an internal wall of a building and the anchor is adapted for location adjacent a wall opening.
 20. An anchor according to claim 1, wherein the wall opening is a window and the safety device supports an operator outside the building. 